Engineer's Tips:
In this month's tip I will explain the importance of "grading and drainage" to the integrity of a house.

I see cracks? I am often asked by clients about unsightly cracks in a houses components caused by differential settlement problems present in a house's foundation.  Most of the differential settlement I've seen in a house's foundation is nothing of any serious structural concern.  It usually isn't anything that really threatens the structural integrity of the house, (in layman's terms, the house isn't going to collapse).  But the the differential settlement does cause some serious aesthetic issues in the house.  It results in cracks in brick veneers, sheet rock walls, sheet rock ceilings, cracks in concrete floors, bumps in floors, uneven walking surfaces and sometimes spawling of concrete and tile grout.  These problems are just unsightly or look real bad, they are easily seen when they occur and are difficult and expensive to permanently fix so that they do not reoccur.

How do these problems occur?  Why do they occur?  Well, in the Amarillo, Texas area the prevalent soil type is a sandy clay loam.  The key word here is "clay".  There is a large amount of clay present in the soil making this soil type what engineers call "expansive".  This means that when the soil becomes saturated with water it will swell or expand.  When it dries out again, it will shrink.  The shrinking effect can easily be seen when you see the cracking or clodding of the soil into "alligator cracks" resembling the bumpy rough scaly skin of the alligator.  This swelling and shrinking of the soil wouldn't be a problem if it occurred uniformly across the entire foundation.  The problem arises when it occurs unevenly across the foundation with one part swelling and heaving upwards while another part remains dry or swells to a lesser degree, while still other parts may dry out and shrink back while another part might remain wet and swollen.  This causes the foundation to be pushed upwards in some parts while other parts are shrinking downwards.  This effect is known as "differential settlement".  These differential stresses across the concrete foundation and the house is what causes the unsightly cracking in concrete floors, sheetrock and brick veneers.

What can be done to fix the problem?  They say an ounce of prevention is worth a pound of cure.  As a home owner it is too late to do anything about the design of the house's foundation to deal with the expansive soil, but you can minimize the amount of water that the soil around your foundation comes in contact with.  This is achieved by proper "grading and drainage".  The goal is to minimize ponding against the house and to move water away from the foundation.  Large amounts of water ponding against the house is what saturates the soil.  Side yards should be sloped to drain away from the house, and then should drain either to the front of the house, rear of the house or both.  The front yard should drain away from the house and the back yard should drain away from the house.   No water should ever drain to the house.  Gutters should be installed on the eaves of the house to carry roof drainage to a point where it will adequately drain away from the house as well.  A common problem in this area is that the ground is often level around a house and the side yards do not drain very well, often causing ponding problems against the foundation.  This can be minimized or overcome by adding gutters on the sides of the house to bring the concentrated flows from roof runoff to the front or back of the house where there is a positive slope away from the house and it can then drain away.

What about flowerbeds and sprinklers etc.?  Flowerbeds are not a problem if they drain once the two or three inches of topsoil become saturated.  If there are weep holes in edging and they don't repeatedly retain water against the house then they are OK?  Homeowners should insure that any excess water does drain away from the house.  The same goes for yard sprinkler systems.  Once the yard becomes saturated, the water should run off and not pond against the house.  (Actually if the water is running off, then the topsoil is saturated and you are over watering and wasting water anyway.  In this case you might want to reduce your watering time.)